Storing value in 2d array variable during runtime in c++ - c++

Question

My main code is .ino file for STM32F103C8T6 with STM32 official core. I have also included my library files of .h file and .cpp file.
I want store a values in 2d array called uint32_t Page[15][14]; in .h file of my library
How to store a value in 2d array variable during runtime. I have posted my code below. For me the code below is perfect, but still did not print the value stored in the array by calling the function HatriX_Signal with correct parameters. Kindly let me know what is wrong in my code below.
// .ino file
#include "HATRIX.h"
HATRIX Hatrix;
void setup()
{
Hatrix.HATRIX_INIT(115200);
}
void loop()
{
Hatrix.HatriX_Signal(Temperature_Signal, 0x66, Page[2][0]);
Serial.println(Page[2][0]);
Serial.println((float)Page[2][0] / 100);
}
// .h file
#ifndef HATRIX_H
#define HATRIX_H
#include "Arduino.h"
#include "Thermo_Couple_Input.h"
#define Number_of_Pages 15
#define Number_of_Bytes_Per_Page 64
static Thermo_Couple_Input TC_IN;
static uint32_t Page[Number_of_Pages][(Number_of_Bytes_Per_Page / 4) - 2];
enum Signal { Temperature_Signal,
Pressure_Signal,
Co2_Signal,
Analog_Industrial_Input_Signal,
General_Purpose_Output_Signal,
PWM_Power_Signal,
PWM_Voltage_Signal
};
class HATRIX
{
public:
void HATRIX_INIT(uint32_t bauderate);
void HatriX_Signal(uint8_t Signal, uint8_t I2C_Address, uint32_t Page);
};
#endif
// .cpp file
#include "HATRIX.h"
void HATRIX::HATRIX_INIT(uint32_t bauderate)
{
Serial.begin(bauderate);
}
// \brief Note: The value we get from Thermocouple is float value. So, we multiply the value with 100 and store it in specified static uint32_t Page by user.
// \param enum_Signal choose accordingly from enum signal: { Temperature_Signal ,
// Pressure_Signal ,
// Hatrix.Co2_Signal ,
// Analog_Industrial_Input_Signal ,
// General_Purpose_Output_Signal ,
// PWM_Power_Signal ,
// PWM_Voltage_Signal };
// \param I2C_Address Address of I2C to get the temperature from desired Thermocouple.
// \param Page Give the Page details to store your value. example: Hatrix.Page[4][3]
void HATRIX::HatriX_Signal(uint8_t signal, uint8_t I2C_Address, uint32_t Page)
{
if(signal == Temperature_Signal);
{
TC_IN.Thermo_Couple_Input_Channel(I2C_Address);
Serial.println("Page");
Page = fThermocoupleTemperature * 100;
Serial.println(Page);
}
}

Answer 1

When calling HATRIX::HatriX_Signal(...), you pass a copy of a uint32_t of the multidimensional array Hatrix.Page to the function.
Inside the HATRIX::HatriX_Signal(...) function, you assign a new value to this variable called Page. But since it's just a copy of the value from the array, the array itself won't be effected by this.
In order to get the value of the function you can either use a pointer to the value in the array or a reference to the value in the array, preferably, return the value directly.
Your function could either look like this using a pointer:
void HATRIX::HatriX_Signal(uint8_t signal, uint8_t I2C_Address, uint32_t* Page)
{
if(signal == Temperature_Signal);
{
TC_IN.Thermo_Couple_Input_Channel(I2C_Address);
TC_IN.fThermocoupleTemperature = TC_IN.fThermocoupleTemperature * 100;
Serial.println("Page");
*Page = TC_IN.fThermocoupleTemperature;
Serial.println(*Page);
}
}
and called like:
Hatrix.HatriX_Signal(Hatrix.Temperature_Signal, 0x66, &Hatrix.Page[2][0]);
or look like this using a reference:
void HATRIX::HatriX_Signal(uint8_t signal, uint8_t I2C_Address, uint32_t& Page)
{
if(signal == Temperature_Signal);
{
TC_IN.Thermo_Couple_Input_Channel(I2C_Address);
TC_IN.fThermocoupleTemperature = TC_IN.fThermocoupleTemperature * 100;
Serial.println("Page");
Page = TC_IN.fThermocoupleTemperature;
Serial.println(Page);
}
}
and called like:
Hatrix.HatriX_Signal(Hatrix.Temperature_Signal, 0x66, Hatrix.Page[2][0]);
or alternatively, as I would advice, look like this:
uint32_t HATRIX::HatriX_Signal(uint8_t signal, uint8_t I2C_Address)
{
if(signal == Temperature_Signal);
{
TC_IN.Thermo_Couple_Input_Channel(I2C_Address);
TC_IN.fThermocoupleTemperature = TC_IN.fThermocoupleTemperature * 100;
Serial.println("Page");
uint32_t page = TC_IN.fThermocoupleTemperature;
Serial.println(page);
return page;
}
}
and called like:
Hatrix.Page[2][0] = Hatrix.HatriX_Signal(Hatrix.Temperature_Signal, 0x66);

Answer 2

How to fix this program:
Raw data such as this 2D array should be made private, as per the fundamental OO principle of private encapsulation.
Should you wish the user to access this array it should be done through a "setter" function taking (x,y) coordinates.
Provide a similar "getter" function for read/print access.
HatriX_Signal and similar should not pass along a pointer to data in a class member, because that's nonsense. You already have access to that data through the this pointer.
Generally, I'd advise to read a beginner-level book about C++ and OO, or alternatively ditch C++ completely if you have no intention of using OO program design anyhow.